Light diffusing substrate, transmission screen, and display device

ABSTRACT

A transmission screen includes a Fresnel lens sheet through which light is projected from a projector to a lenticular lens sheet arranged on a viewer side, as approximately parallel light, and the lenticular lens sheet receiving light passing through the Fresnel lens sheet, and emitting the approximately parallel light while horizontally widening, by means of a group of cylindrical lenses which are horizontally in parallel, wherein in at least one of the Fresnel lens sheet and the lenticular lens sheet, on a surface of a light diffusing substrate, in which a light diffusing material is dispersed, irregularities which constitute a lens section is formed, and in the light diffusing substrate, dispersion density of the light diffusing material differs in at least two layers in the thickness direction.

CROSS REFERENCE TO RELATED APPLICATION

This application is a Divisional of application Ser. No. 10/645,880filed Aug. 22, 2003, now U.S. Pat. No. 6,984,046, and incorporated byreference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display device such asrear-projection screen television, a transmission screen used for thedisplay device, and a light diffusing substrate constituting the screen.

2. Description of Related Art

As one conventional transmission screen, there is known for example asshown in FIG. 2, a transmission screen which is generally used for arear-projection screen television equipped with a CRT projector.

The screen normally includes in sequence from the viewer side, at leasttwo lens sheet members, namely a dual-surface lenticular lens sheet 20and a Fresnel lens sheet 10. In some cases, a flat protection sheet 30is arranged at an outermost position on the viewer side.

The dual-surface lenticular lens sheet 20 is a lenticular lens sheetconfigured by forming on both sides, lens sections 22 and 23 of multipleoblong cylindrical lenses with the vertical direction as thelongitudinal direction continuously arrayed in a horizontal direction.The lens section 22 on the projector side has a function for refractingand diffusing in the vertical direction image light projected from theprojector, and the other lens section 23 on the viewer side has afunction for modifying color shift (a problem of color shift of outgoinglight attributable to a three-tube projector being arranged off-axis) bysynergism with the lens section on the projector side.

On the other hand, for the image light to be seen by the viewer it isnecessary to expand the viewing area not only in the horizontaldirection but also in the vertical direction. In the vertical direction,the viewing area is expanded not by the refracting and diffusingfunction of the lens but by the diffusing function of a light diffusingmaterial, and a method for applying the light diffusing material 24 tothe lenticular lens sheet is employed.

In application of the light diffusing material, techniques have beenappropriately employed such as, mixing the light diffusing material intothe lenticular lens sheet itself to diffuse the light diffusing materialinto the interior of the lens sheet, or spread forming on the lenticularlens sheet, as a different member to the lens sheet, an ink containingthe light diffusing material, or laminating on the lenticular lens sheeta resin sheet which has been extrusion formed with the light diffusingmaterial mixed therein.

Furthermore, a typical configuration is where convex parts are providedat the boundaries of the cylindrical lenses on the viewing surface sideof the dual-surface lenticular lens sheet, and a shading layer 25 isformed by printing or transfer forming a black ink onto the flat portionof the apexes thereof.

The main purpose for forming the shading layer 25 is to improve thecontrast of the image seen, and to absorb external light so thatreflection on the screen surface is not seen by the viewer.

In the dual-surface lenticular lens sheet 20, since there areirregularities on the exposed viewing surface side, dust and dirt areeasily attached. Therefore, in some cases a protection sheet 30 isarranged for preventing the attachment of dust and dirt, and forprotecting the shading layer.

Normally, on the surface of the protection sheet 31, it is general toprovide a surface treatment layer 38 such as a hard coat for excoriationresistance, or an antistatic treated layer, or the like.

Recently, rather than the rear-projection screen television equippedwith a CRT projector (hereunder called a CRT projection-type rearprojection television), a rear-projection screen television equippedwith a liquid crystal projector (hereunder called a liquid crystalprojection-type rear projection television) having characteristics suchas less power consumption, light weight, and thinness, has becomepopular.

Specifically, with upgrading of the image source such as to correspondto digital high definition, development of television of a format whichuses the high definition liquid crystal panel is flourishing. Also in aliquid crystal projection-type rear projection television, atransmission screen that is bright with high resolution, that has a wideviewing angle in both the horizontal and vertical directions, that issuperior in contrast, and that enables viewing of sharp images, has beensought.

In the case of the CRT projection-type rear projection television, asmentioned above, in order to correct for color shift caused bypositional differences of the respective three tubes of RGB after imagelight is projected by means of the three tubes, the dual-surfacelenticular lens sheet is used for the transmission screen. On the otherhand, in the case of the liquid crystal projection-type rear projectiontelevision, the image light regulated by the liquid crystal panel isprojected through a monocular lens, and so that color shift caused bypositional differences does not occur, a single face lenticular lenssheet having a lens section on only one surface can be used for thetransmission screen.

An example of the transmission screen used for the liquid crystalprojection-type rear projection television is shown in FIG. 3.

The screen is configured by at least two members, namely a lenticularlens sheet 70 and a Fresnel lens sheet 60.

The lenticular lens sheet 70 is generally of a configuration where alens section of multiple oblong cylindrical lenses with the verticaldirection as the longitudinal direction continuously arrayed in ahorizontal direction of the screen face, is formed on only one surface(single face lenticular lens sheet), and has a function for refractingand diffusing image light in the vertical direction.

On the flat surface on the opposite side to the lens section, whichbecomes the viewer side, a shading layer 75 is formed similarly to thecase of the dual-surface lenticular lens sheet, to prevent reflectiondue to external light and improve the contrast of the image seen.

Furthermore, similarly to the case of the CRT projection-type rearprojection television, it is necessary to widen the viewing area by thediffusing function of the light diffusing material, and a method forapplying a light diffusing material to the lenticular lens sheet isemployed.

The present applicant has proposed a lenticular lens sheet of aconfiguration where a light diffusing layer is formed on a shading layerof a single face lenticular lens sheet on Japanese Unexamined PatentApplication, First Publication No. H09-120101.

As a light diffusing layer 80, techniques have been appropriatelyemployed such as, spread forming ink containing the light diffusingmaterial on the shading layer of the lenticular lens sheet, orlaminating on the lenticular lens sheet a resin sheet (diffusing sheet)84 which has been extrusion formed with the light diffusing materialmixed therein.

In the latter, when the separately manufactured diffusing sheet 81 isadhered via an adhesion layer 87 to the lenticular lens sheet 70, it hasthe dual function of also imparting rigidity to the lenticular lenssheet.

The same figure gives a description related to the light diffusing layer80 where a surface treatment layer 88 that effects a desired surfacetreatment (hard coat, antistatic, antireflection), is formed asnecessary on the surface of the diffusing sheet 81.

In the light diffusing sheet 81 in which the light diffusing material isdispersingly mixed, the light diffusing material 84 is exposed from thesurface, so the surface smoothness of the diffusing sheet is low.

Therefore, when the diffusing sheet 80 is laminated to the lenticularlens sheet 70, there are problems with handling such as, cohesiveness isnot good, and selection of the adhesive 87 is limited.

As a patent application related to the light diffusing layer for thescreen, Japanese Unexamined Patent Application, First Publication No.H11-271510 by the present applicant is well-known.

The above patent application is “a light diffusing sheet characterizedin being formed by a three-layer configuration where front and backexternal layers are an optical transmittable resin, and an intermediatelayer is an optical transmittable resin in which diffusive particles aredispersed.” The problems to be solved in this application are, a problemthat in the case where an optical transmittable resin (intermediatelayer) in which diffusive particles are dispersed, is laminated via anadhesive to another screen member (such as a lenticular lens sheet), thelight diffusion characteristics change from the initial characteristicsdue to the influence of the adhesive; or a problem of adhesivenessbetween the light diffusing sheet and the other screen member when asurface condition is formed where the diffusive particles protrude fromthe intermediate layer. Since there is uncertainty about durability, andenvironmental changes such as temperature and humidity, the intermediatelayer is protected and the smoothness of the surface is maintained bythe optical transmittable resin of the front and back external layers.

Incidentally, there has been a demand for a light diffusing layer whichis appropriate for screens in order to deal with problems peculiar toliquid crystal projection-type rear projection televisions.

In the liquid crystal projector, since the diameter of the projectionpupil of the projection lens is small, then compared to the CRTprojector, the following phenomena are noticeable.

A “hot bar” phenomenon where the brightness of the central point ofincident light from the projector becomes a local high (hotspot), andbright stripes are observed in the direction of the parallel arrangementof the cylindrical lenses.

A “scintillation” phenomenon which is unnecessary flicker seen in theprojected image.

In order to avoid hot bar, it is necessary to raise the light diffusion,and it is necessary to raise the light diffusion in a direction(vertical direction) perpendicular to the direction of the parallelarrangement of the cylindrical lenses.

Therefore, a proposal to enlarge the thickness of the light diffusinglayer has been made by the present applicant as disclosed in JapaneseUnexamined Patent Application, First Publication No. H10-83029.

On the other hand, in order to achieve high-definition of the imagequality, it is desirable that the light diffusing layer be as thin aspossible without causing a drop in resolution, resulting in aconfiguration in conflict with avoiding hot bar.

The present invention takes into consideration the above problems withthe object of providing at a comparatively low cost a transmissionscreen, as a screen for a projection-type rear projection television(specifically, which uses a high-definition liquid crystal panel), thatis bright with high resolution, that has a wide viewing angle in boththe horizontal and vertical directions, that is superior in contrast,that enables viewing of sharp images, and further that reduces colorshift.

SUMMARY OF THE INVENTION

The first aspect of the present invention is a transmission screenhaving a Fresnel lens sheet through which light is projected from aprojector to a lenticular lens sheet arranged on a viewer side, asapproximately parallel light, and the lenticular lens sheet receivinglight passing through the Fresnel lens sheet, and emitting theapproximately parallel light while horizontally widening, by means of agroup of cylindrical lenses which are horizontally in parallel, whereinin at least one of the Fresnel lens sheet and the lenticular lens sheet,on a surface of a light diffusing substrate, in which a light diffusingmaterial is dispersed, irregularities which constitute a lens section isformed, and in the light diffusing substrate, dispersion density of thelight diffusing material differs in at least two layers in the thicknessdirection.

The light diffusing substrate may be spread formed with ink containingthe light diffusing material on at least one surface of a resin sheetextrusion formed with the light diffusing material mixed therein.Furthermore, the light diffusing substrate may have laminated on thesurface of the resin sheet extrusion formed with the light diffusingmaterial mixed therein, another resin sheet extrusion formed with adifferent density of the light diffusing material mixed therein.

Moreover, on one surface of a transparent resin substrate which does notcontain the light diffusing material, may be laminated at least twolayers of resin layers containing the light diffusing material.

Furthermore, the dispersion density of the light diffusing material ispreferably higher on the side of the projector than on the viewer side.

Moreover, in a multilayer configuration of the at least two layers,preferably the light diffusing material dispersed on the projector sideis mainly composed of an inorganic material, and the light diffusingmaterial dispersed on the viewer side is mainly composed of an organicmaterial. Furthermore, preferably the light diffusing material dispersedon the Fresnel lens sheet side is an organic material, and the lightdiffusing material dispersed on the lenticular lens sheet side is aninorganic material.

Moreover, the surface on the viewer side of the light diffusingsubstrate may be subjected to at least one surface treatment selectedfrom hard coat treatment, antistatic treatment, and antireflectiontreatment. Furthermore the surface on the viewer side of the resin sheetextrusion formed with the light diffusing material mixed therein, may besubjected to at least one surface treatment selected from hard coattreatment, antistatic treatment, and antireflection treatment.

The second aspect of the present invention is a transmission screenhaving a Fresnel lens sheet through which light is projected from aprojector to a lenticular lens sheet arranged on a viewer side, asapproximately parallel light, and the lenticular lens sheet receivinglight passing through the Fresnel lens sheet, and emitting theapproximately parallel light while horizontally widening, by means of agroup of cylindrical lenses which are horizontally in parallel, whereinin the Fresnel lens sheet on one surface of a light diffusing substrate,in which a light diffusing material is dispersed, irregularities whichconstitute a lens section including a reacted product of aradioactive-ray-curable-resin is formed, and on the other surface,irregularities which constitute a lens section which light is verticallywidened and projected from the projector is formed, by means of a groupof the cylindrical lenses which are vertically in parallel, and in thelenticular lens sheet, on one surface of a substrate on the Fresnel lenssheet side, the group of cylindrical lenses which are horizontally inparallel is formed by a reacted product of aradioactive-ray-curable-resin, and on the other surface, at a positioncorresponding to the boundaries of the cylindrical lenses, astripe-shaped shading layer is formed, and a light diffusing substratemade by laminating at least two layers of resin layers containing thelight diffusing material on one surface of a transparent resin substratewhich does not contain the light diffusing material, is laminated sothat the side which does not contain the light diffusing material facesto the shading layer side, and in the resin layer, a dispersion densityof the light diffusing material differs in at least two layers in thethickness direction.

The third aspect of the present invention is a transmission screenhaving a Fresnel lens sheet through which light is projected from aprojector to a lenticular lens sheet arranged on a viewer side, asapproximately parallel light, and the lenticular lens sheet receivinglight passing through the Fresnel lens sheet, and emitting theapproximately parallel light while horizontally widening, by means of agroup of cylindrical lenses which are horizontally in parallel, whereinthe lenticular lens sheet is formed with irregularities which constitutea lens section on the surface of a light diffusing substrate having alight diffusing layer, the light diffusing substrate is mainly composedof an organic material, the light diffusing layer contains at least twokinds of light diffusing material which differ at least in any one ofshape, mean particle diameter, and material, and at least one kind oflight diffusing material of the light diffusing materials comprises aninorganic material.

In the case where the shapes of at least two kinds of light diffusingmaterial contained in the light diffusing layer are globular, the lightdiffusing layer may contain a first light diffusing material with a meanparticle diameter satisfying a range of 1 to 10 mm and a second lightdiffusing material with a mean particle diameter satisfying a range of20 to 50 mm.

Furthermore, in the case where at least one kind of light diffusingmaterial contained in the light diffusing layer includes an organicmaterial, the mean particle diameter of the organic light diffusingmaterial is preferably larger than the mean particle diameter of aninorganic diffusing agent where the light diffusing material comprisesan inorganic material.

Moreover, the at least two kinds of light diffusing material whichdiffer at least in any one of shape, mean particle diameter, andmaterial, contained in the light diffusing layer, may further contain aninorganic light diffusing material of irregular shape.

According to the above aspects, by combining a Fresnel lens sheet with alenticular lens sheet which contains in the interior of the basematerial two or more kinds of light diffusing material which differ atleast in any one of shape, mean particle diameter, and material, andwhich has a light diffusing layer where at least one kind of lightdiffusing material of the light diffusing materials comprises aninorganic material, a transmission screen with good dispersibility ofthe light diffusing material and that reduces color shift can berealized.

The fourth aspect of the present invention is that in the abovementionedtransmission screen, a refractive index of a resin constituting thelight diffusing substrate is higher than a refractive index of the lightdiffusing material.

Furthermore, a refractive index ratio of the resin and the lightdiffusing material is preferably in a range of resin: light diffusingmaterial=1:0.7 to 1. Moreover a refractive index difference of the resinand the light diffusing material is preferably in a range of 0 to 0.2.

Furthermore, a thickness of the light diffusing layer may be in a rangeof 1 to 60 μm, a dosage of the light diffusing material may be in arange of 5 to 40 parts by weight for 100 parts by weight of the lightdiffusing layer, and a mean particle diameter of the light diffusingmaterial may be in a range of 1 to 30 μm, and a standard deviation ofthe mean particle diameter according to a laser diffraction scatteringmethod may be less than 6 μm.

According to the above aspects, in the transmission screen, by settingthe refractive index of the transmissive resin other than the lightdiffusing material constituting the light diffusing layer higher thanthe refractive index of the particles, then even for a thinner screenwhich uses a projector using a high-intensity light source, a lightdiffusion screen where hot bar is reduced and scintillation is mitigatedcan be realized.

The fifth aspect of the present invention is a display device of a typewhich forms a display light by projecting an illumination light ontoimage display elements in which a display image is regulated bytransmission/non transmission (or, transmission /light diffusion) orselective reflection, and is equipped with the above transmissionscreen, either alone or in combination with another lens sheet.

The sixth aspect of the present invention is a light diffusing substratehaving a light diffusing layer made by dispersing and mixing a lightdiffusing material into a resin, and in the light diffusing layer, adispersion density of the light diffusing material differs in at leasttwo layers in the thickness direction.

According to the above aspect, since the light diffusing layer is amultilayer configuration, then this is ideal for the whole of the lightdiffusing substrate, or for when desirably controlling the lightdiffusion characteristic corresponding to the lens characteristic of thelens sheet.

Furthermore, if it is a light diffusing layer constituted by only onelayer having a uniform dispersion density of the light diffusingmaterial, then in the case where it has sufficient light diffusivity forpractical use, if the mixed quantity of the light diffusing materialincreases, irregularities on the surface become noticeable whichpresents a rough appearance, and the reflectivity of the external lightbecomes higher. However, by arranging the light diffusing layer of a lowdensity on the viewer side, the appearance becomes one with a moderatematte look and moderate reflectivity of external light.

The seventh aspect of the present invention is a light diffusingsubstrate having a light diffusing layer made by dispersing and mixing alight diffusing material into a resin, wherein the light diffusingsubstrate is mainly composed of an organic material, the light diffusinglayer contains at least two kinds of light diffusing material whichdiffer at least in any one of shape, mean particle diameter, andmaterial, and at least one kind of light diffusing material of the lightdiffusing materials comprises an inorganic material.

According to the embodiment, since it contains in the interior of thelight diffusing substrate, two or more kinds of light diffusing materialwhich differ at least in any one of shape, mean particle diameter, andmaterial, and has a light diffusing layer where at least one kind oflight diffusing material of the light diffusing materials comprises aninorganic material, then this is ideal for the whole of the lightdiffusing substrate, or for when desirably controlling the lightdiffusion characteristic corresponding to the lens characteristic of thelens sheet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A and FIG. 1B are explanatory diagrams showing an example of aconfiguration of a transmission screen of a first embodiment of thepresent invention, FIG. 1A being a perspective view and FIG. 1B being across-section on the X-Y plane.

FIG. 2 is a cross-section showing a configuration of a transmissionscreen used for a CRT projection-type rear projection television.

FIG. 3 is a cross-section showing a configuration of a transmissionscreen used for a liquid crystal projection-type rear projectiontelevision.

FIG. 4 differs from the present invention, and is an explanatory diagramshowing a transmission screen related to a configuration in contrast tothe screen shown in FIG. 1A and FIG. 1B.

FIG. 5 is a graph showing a relation between screen viewing direction(angle of view) and viewing brightness.

FIG. 6 is an explanatory diagram schematically showing that in the casewhere a light diffusing layer is on a viewer side, the horizontalviewing angle is widened by light diffusion.

FIG. 7 is a table showing screen characteristics for the respectiveexamples and comparison examples.

FIG. 8A is a perspective view showing an example of a transmissionscreen of a second embodiment of the present invention, and FIG. 8B is across-section on A–A′ of the lenticular lens sheet of the presentinvention shown in FIG. 8A.

FIG. 9 is a cross-section on A–A′ showing a different configuration ofthe lenticular lens sheet as an embodiment of the present invention.

FIG. 10 is a cross-section on A–A′ showing a different configuration ofthe lenticular lens sheet as an embodiment of the present invention.

FIG. 11 is a cross-section on A–A′ showing a different configuration ofthe lenticular lens sheet as an embodiment of the present invention.

FIG. 12 is a cross-section on A–A′ showing a different configuration ofthe lenticular lens sheet as an embodiment of the present invention.

FIG. 13 is an explanatory diagram for explaining a condition whereprojected light incident from a projector to a transmission screenhaving a light diffusing layer essentially containing an inorganic lightdiffusing material in the present invention, is dispersed by the lightdiffusing material, and reaches to the viewer side.

FIG. 14 is an explanatory diagram for explaining a condition whereprojected light incident from a projector to a transmission screen notusing light diffusing material, is not dispersed by a light diffusingmaterial, and directly reaches to the viewer side.

FIG. 15 is an explanatory diagram for explaining a condition whereprojected light incident from a projector to a transmission screenhaving a light diffusing layer composed of organic light diffusingmaterial, is diffused by the light diffusing material, and reaches tothe viewer side.

FIG. 16 is a schematic diagram for comparing diffusion angles of atransmission screen having a light diffusing layer including aninorganic light diffusing material of an irregular shape, and atransmission screen having a light diffusing layer including a globularorganic light diffusing material.

FIG. 17 is a graph showing chromaticity of an XYZ calorimetric system(x, y) which becomes a base for respective colorimetric systems as a CIEstandard calorimetric system.

FIG. 18 is a cross-section of a liquid crystal projection-type rearprojection television which is an example of a display device of afourth embodiment of the present invention.

FIG. 19A and FIG. 19B are cross-sections showing a configuration of atransmission screen of another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereunder is a description of a first embodiment of the presentinvention.

In the following description, a lenticular (lens section) having afunction for refracting an incident light in a horizontal direction iscalled a “horizontal lenticular” and a lenticular (lens section) havinga function for refracting in a vertical direction is called a “verticallenticular.”

FIG. 1A and FIG. 1B are explanatory diagrams showing an example of aconfiguration of a transmission screen of the present invention, FIG. 1Abeing a perspective view and FIG. 1B being a cross-section on the X-Yplane.

In a Fresnel lens sheet 90, on one surface of a light diffusingsubstrate 91 (non projector side) is formed a lens section 92 having aresin such as a reacted product of a radiation ray-curable-resin. On theother surface (projector side), a vertical lenticular 93 is formed.

Examples of resin base material constituting the, light diffusingsubstrate 91 include polyester resin, styrene resin, acrylic resin,acrylic-styrene copolymer, polycarbonate resin, vinyl chloride resinsheet, and the like. However, it is not specifically limited.

Furthermore, in the resin base material, a light diffusing material 94which is mainly composed of globular glass beads or resin crosslinkbeads of a particle size of 1 to 30 μm is dispersingly mixed.

In a horizontal lenticular lens sheet 100, on the Fresnel lens sheetside of a substrate 101, a group of cylindrical lenses 102 is formed bya resin such as a reacted product of a radioactive-ray-curable-resin. Onthe other surface, in a position corresponding to a boundary of thecylindrical lens, a stripe-shaped shading layer 105 is formed, on whicha light diffusing layer (light diffusing substrate) 200 is laminated.

For the substrate 101, similarly to the above, the material includespolyester resin, styrene resin, acrylic resin, acrylic-styrenecopolymer, polycarbonate resin, vinyl chloride resin sheet, and thelike. However, the material is not limited to these.

The light diffusing substrate 200 has a configuration where on onesurface of a transparent resin substrate 201 which does not contain alight diffusing material, two or more layers of a resin layer (lightdiffusing layer) 208 containing a light diffusing material arelaminated, and is laminated via an adhesive layer 207 so that the sidewhich does not contain a light diffusing material faces to theaforementioned shading layer 105 side.

As the resin base material constituting the light diffusing substrate200, resin board that has rigidity and excellent light transmittance,such as acrylic resin, acrylic-styrene copolymer (MS resin), andpolycarbonate resin may be used, however, it is not specificallylimited.

The light diffusing layer 208 has a configuration where the dispersiondensity of the light diffusing material differs over two or more layersin the substrate thickness direction. This is shown enlarged in the samedrawing.

In the present embodiment, on the transparent substrate 201, a firstlight diffusing layer and second light diffusing layer are formed inthis sequence. For the second light diffusing layer, there is a casewhere it concurrently functions as a hard coat layer being one of thesurface treatments. In a formula for formula forming the second lightdiffusing layer, a filler for imparting abrasion resistance is includedin addition to the light diffusing material.

The first light diffusing layer is formed by coating at a film thicknessof around 20 μm, an acrylic resin in which inorganic diffusing agentsuch as silica is dispersed at a density of 30%.

The second light diffusing layer is formed by coating at a filmthickness of around 20 μm, an acrylic resin in which organic bridgebeads such as acrylic or MS are dispersed at a density of 15%.

The second light diffusing layer is not limited to that mentioned above(hard coat treatment), and may concurrently have various functions suchas antistatic treatment, or antireflection treatment.

Furthermore, in some cases ultraviolet-curing-paint is used for thefirst and second light diffusing layer.

The ultraviolet-curing-paint is mainly composed of a polymer, oligomer,monomer, or the like, which generally has a radical polymeric doublebond or epoxy radical within the structure as a film forming component,and besides contains a photoinitiator or sensitizer.

Preferably, by using a polyfunctional (meta) acrylateultraviolet-ray-curable-paint in which the film forming component has anacrylate functional group, then specifically, a hard coat layer of thesecond layer which is superior in surface hardness, transparency,friction-resistance, and abrasion resistance may be formed concurrentlywith the diffusing layer.

In the method for applying the ultraviolet-ray-curable-paint on theresin board, specifically, gravure coating, gravure reverse coating,reverse roll coating, offset gravure coating which are superior in theaccuracy of application thickness, the smoothness of applicationsurface, and the like are preferable.

Furthermore, by using a transfer sheet where a hard coat layer is atransfer layer, it may be formed by transferring.

In the case where the second light diffusing layer made byultraviolet-ray-curable-paint concurrently performs light diffusion,hard coat, and antistatic, then in general a fine powder such as asurfactant is added to the ultraviolet-ray-curable acrylic resin as anantistatic agent. The kind of antistatic agent, and the dosage are notspecifically limited.

As an antireflection layer, on the surface of the second light diffusinglayer, a film composed of a low refractive index material, a transparentfluorocarbon resin, or a fluorocarbon inorganic compound, may be formedinto a light diffusing substrate by application or vapor deposition,however, the low refractive index material or the forming method are notspecifically limited. As a result, the external light contrast isimproved and the image can be viewed without reflection.

The light diffusing layer, from the point of light diffusioncharacteristics and rigidity, generally requires a thickness of around0.5 to 2 mm.

In the case of the above embodiment, the light diffusing substrate 91 inthe Fresnel lens sheet 90 is a resin layer (light diffusing layer) thewhole of which contains light diffusing material. However, in the lightdiffusing substrate 200, the most part is formed by the transparentresin substrate 201, and the light diffusing layer 208 is in a thicknessratio of no more than a part (around 20 to 100 μm) of the whole body.

In the light diffusing layer, there are various limitations regardingfor example, the refractive index difference between the light diffusingmaterial (particle) and the resin into which it is dispersing and mixed,and the preferable combinations and forming methods from the point ofdispersing and mixing the ingredients evenly for the whole body. Asheet-like light diffusing substrate, where the whole body includes alight diffusing layer with a thickness having sufficient rigidity(around 0.5 to 2 mm), occupies a high proportion of the cost of thewhole screen.

According to the configuration of the above embodiment, a lightdiffusing substrate the whole of which includes a light diffusing layeris only on the Fresnel lens sheet 90 side, and a substrate on thehorizontal lenticular lens sheet 100 side has a low cost configuration,and the light diffusing layer is comparably thin. Consequently, thehigh-definition of the image quality can be achieved without decreasingdisplay brightness or resolution.

The light diffusing layer on the horizontal lenticular lens sheet 100side has a multilayer configuration, and control of the light diffusioncharacteristic is facilitated by combinations thereof. Therefore thevertical light diffusion characteristic particularly for the important“hot bar avoidance”, can be controlled by also including a combinationof pitch and lens characteristic (range of emission angles) of thevertical lenticular 93 in the Fresnel lens sheet 90.

Furthermore, due to the synergism of the refracting and diffusingfunction of the vertical image light corresponding to the verticallenticular 93 in the Fresnel lens sheet 90, and the refracting anddiffusing function in the horizontal direction due to the horizontallenticular lens sheet 100, the quantity of light of the screen displaycan be controlled evenly so that a screen of even brightness can beobtained.

The light diffusing material (particles) 94 constituting the lightdiffusing substrate 91 in the Fresnel lens sheet 90 is mainly in theform of globules of organic light diffusing material with a particlediameter of 10 to 100 μm.

The reason why the abovementioned are preferable as the light diffusingmaterial on the Fresnel lens sheet side is that with an inorganic lightdiffusing material the form is generally irregular, which causes randomlight diffusion. As a result, when it is used on the Fresnel lens sheetside, the projected light from projector is randomly diffused and thenshone into the Fresnel lens section, so that the characteristics due tothe Fresnel lens sheet are spoiled.

However, with a light diffusing material composed of an organicdiffusing agent, it is easy to obtain the globular and uniform shape, sothat the characteristics due to the Fresnel lens sheet are not spoiled,and this is thus preferable when emitting onto the horizontal lenticularlens sheet side.

Transmitted light (La) of projected light from the projector which haspassed through the light diffusing layer of the Fresnel lens sheet, canbe represented by the sum of parallel light (L1) and diffused light(L2).

The transmitted light (La) has its optical path refracted in the Fresnellens section and is then incident on the lens surface of the horizontallenticular lens sheet, and output to the viewer side.

The transmitted light which has passed through the Fresnel lens sheet,is incident on the lens surface of the horizontal lenticular lens sheet,and then when passing through the screen opening section correspondingto the light-condensing section except for the shading layer 105, theparallel light (L1) component is less than the diffused light (L2)component. Consequently, even in the case where the proportion (BSratio) occupied by the shading layer (BS: black stripe) is more than50%, shading due to the BS are small, the utilization efficiency of theprojected light from the projector is high, and a bright display imagecan be viewed.

The BS ratio (%) is represented by 100× shading section/(openingsection+shading section).

FIG. 4 is an explanatory diagram showing a configuration of a screenusing a substrate 200 which is composed only of a transparent resinsubstrate 201 and does not have a light diffusing layer. It is aconfiguration for comparison with the present invention shown in FIG. 1.In the case where there is no light diffusing layer on the viewer sidefrom the shading layer 105, the larger the angle of view becomes, thenarrower the horizontal viewing angle tends to become.

This is because, comparing the case where a light diffusing layer is onthe viewing surface and the case where it is not, the light which haspassed through the opening section (light passing section of the non BSsection) diffuses more in the former case than in the latter case.Consequently, the viewing angle is enlarged as a whole (refer to FIG. 5and FIG. 6).

FIG. 5 is a graph showing a relation between screen viewing direction(angle of view) and viewing brightness. The solid line denotes thecharacteristics in the case where there is a light diffusing layer onthe viewer side, and the broken line denotes the characteristics in thecase where there is not a light diffusing layer on the viewer side

FIG. 6 is an explanatory diagram schematically showing that in the casewhere a light diffusing layer is on the viewer side, the horizontalviewing angle is widened by light diffusion.

Hereunder is a description of examples of the first embodiment of thepresent invention.

The following is a description comparing examples 1 to 5 where lightdiffusing layers are provided as two-layer structures on a transparentresin substrate, as a light diffusing substrate positioned on the viewerside of the lenticular lens sheet, with comparative example 1 where alight diffusing layer is not provided on the transparent resinsubstrate, and comparative example 2 where a light diffusing material isdispersing and mixed evenly throughout.

EXAMPLE 1

On one surface of a transparent resin substrate (acrylic resin of 2 mmthickness), light diffusing layers as shown in (a) and (b) hereunderwere applied in this sequence and formed. The application thickness was20 μm for both.

-   (a) first light diffusing layer containing organic diffusing agent    at a density of 30%-   (b) second light diffusing layer containing organic diffusing agent    at a density of 15%

EXAMPLE 2

On one surface of a transparent resin substrate (acrylic resin of 2 mmthickness), light diffusing layers as shown in (a) and (b) hereunderwere applied in this sequence and formed. The application thickness was20 μm for both.

-   (a) first light diffusing layer containing organic diffusing agent    at a density of 15%-   (b) second light diffusing layer containing organic diffusing agent    at a density of 30%

EXAMPLE 3

On one surface of a transparent resin substrate (acrylic resin of 2 mmthickness), light diffusing layers as shown in (a) and (b) hereunderwere applied in this sequence and formed. The application thickness was20 μm for both.

-   (a) first light diffusing layer containing organic diffusing agent    at a density of 15%-   (b) second light diffusing layer containing organic diffusing agent    at a density of 15%

EXAMPLE 4

On one surface of a transparent resin substrate (acrylic resin of 2 mmthickness), light diffusing layers as shown in (a) and (b) hereunderwere applied in this sequence and formed. The application thickness was20 μm for both.

-   (a) first light diffusing layer containing inorganic diffusing agent    at a density of 30%-   (b) second light diffusing layer containing organic diffusing agent    at a density of 15%

EXAMPLE 5

On one surface of a transparent resin substrate (acrylic resins of 2 mmthickness), light diffusing layers as shown in (a) and (b) hereunderwere applied in this sequence and formed. The application thickness was20 μm for both.

-   (a) first light diffusing layer containing organic diffusing agent    at a density of 30%-   (b) second light diffusing layer containing inorganic diffusing    agent at a density of 15%

COMPARATIVE EXAMPLE 1

A transparent resin substrate with nothing applied to the surface(acrylic resin of 2 mm thickness).

COMPARATIVE EXAMPLE 2

A resin sheet extrusion formed by mixing organic light diffusingmaterial (MS resin of 2 mm thickness).

Various substrates of configurations related to examples 1 to 5 andcomparative examples 1 and 2 were used as a protection sheet in atransmission screen (conventional transmission screen) for the CRTprotection sheet rear projection television shown in FIG. 2, and therespective screen performances were evaluated.

FIG. 7 is a table showing screen characteristics for the respectiveexamples and comparison examples.

Firstly, when comparing configurations where light diffusing layers areprovided on the viewer side (examples 1 to 5), with a configurationwhere a light diffusing layer is not provided (comparative example 1),in the comparative example 1, it is seen that yH which denotes the widthof the horizontal viewing angle (the angle to give a reduction inbrightness of 1/10 when moving in a transverse direction, with the frontface=0°), and δH (similarly, an angle to give a reduction to 1/20) aresmaller compared to examples 1 to 5.

This means that the height of the bottom part of the curve shown by thedotted line (comparative example 1) in FIG. 5 drops down.

On the other hand, the bottom part of the curve shown by the solid line(examples 1 to 5) maintains a higher brightness than for the dottedline.

The comparison of examples 1 to 5 and comparative example 2 wereevaluated under the item of sharpness, by visual observation of thedisplay image. In the examples 1 to 5, since the light diffusing layerwas obviously thin, image blurring was less and image sharpness washigh.

Next, when comparing between examples 1 to 5, the ones with the lowerdispersion density of the light diffusing material in the second lightdiffusing layer (examples 1, 3, 4, 5) had better surfaces of view thanthe ones with higher dispersion density (example 2), and there was alsothe result of less irregular reflection on the surfaces due to externallight (denoted by external light reflectance). A good or bad ofappearance of the viewing surface was evaluated by visual observation.

So that the appearance of the viewing surface is good, and irregularreflection on the surfaces from external light is low, the dispersiondensity of the light diffusing material in the second light diffusinglayer, which becomes the outer most surface, is preferably around 15%.

In order to widen the viewing angle, the dispersion density of the lightdiffusing material should be high, and preferably around 30% for screenuse.

If the light diffusion characteristic (viewing angle) is given priority,the external appearance is damaged and irregular reflection on thesurface becomes significant, as mentioned above. In order toconcurrently maintain the light diffusion characteristic (viewing angle)and good external appearance, it is preferable that the dispersiondensity of the light diffusing material is lower on the second lightdiffusing layer side and higher on the first light diffusing layer side(examples 1, 4 and 5).

In observation of a projection-type rear projection television (foreither a CRT or liquid crystal), in the case where the light diffusinglayer has a certain thickness, then when viewed from a different angle,a slight color change becomes a problem attributable to the change inthe optical path length (in the line of sight direction) in the lightdiffusing layer.

This is assumed to be because the extent to which the projected displaylight goes via the light diffusing substrate, changes corresponding tothe change in the optical path length (in the line of sight direction)within the light diffusing layer.

The aforementioned color change is expressed in the same diagram as thehorizontal color change (Δx) and the vertical color change (Δy), and thesmaller these are the better.

The examples 1, 2 and 3 are comprised of only organic diffusing agent,while the examples 4 and 5 contain inorganic diffusing agent. It is seenthat the latter show less color change.

This is assumed to be because the inorganic diffusing agent such assilica and alumina has an irregular shape, has larger light diffusion,and is more random than the globular organic diffusing agent as bridgebeads such as acrylic and MS.

In a comparison between examples 4 and 5, it is noticeable that example4 using more of the inorganic diffusing agent with larger lightdiffusion, in the second light diffusing layer, shows less color shift.

The above examples (comparative examples) describe the case wheremultilayer light diffusion by the present invention is applied to atransmission screen (conventional transmission screen) for a CRTrear-projection screen television as shown in FIG. 2. However, thepresent invention is also applicable to a transmission screen for aliquid crystal rear-projection screen television (FIG. 1, FIG. 3).

Specifically, a screen related to the configuration in FIG. 1 ispreferable for application of the present invention.

This is because “the light diffusing substrate included entirely of alight diffusing layer made by extrusion forming” used on both theFresnel lens sheet side and the horizontal lenticular lens sheet side asabove described, is applied to only one side (the Fresnel lens sheetside), and hence the cost for the horizontal lenticular lens sheet sidecan be reduced.

In this case, with a thickness of the light diffusing layer in an amountfor applying and forming on one side of the transparent resin substrate,specifically in the vertical direction, the viewing angle is notsufficiently widened. Consequently, a screen related to theconfiguration of FIG. 1 using a Fresnel lens sheet on which a verticallenticular is formed on the projector side, demonstrates the bestoperation and effect by the present invention.

Next is a description of a second embodiment of the present invention.

FIG. 8 is a perspective view showing an example of a transmission screenwhich is formed by combination of a Fresnel lens sheet with a lenticularlens sheet of the present invention.

As shown in FIG. 8A, there is shown an example of a transmission screenof a configuration combined and arranged such that; by using alenticular lens sheet 1 of the present invention, a stripe-shapedshading layer 3 is provided in an area where image light does not pass,and a Fresnel lens sheet 2 is combined so that the light diffusing layerof the lenticular lens sheet faces to the viewer side and the Fresnellens sheet faces to the projector side. FIG. 8B shows a cross-section onA–A′ of the lenticular lens sheet of the present invention, showing anexample of a configuration where on one surface of a base material 5 inwhich two kinds of inorganic light diffusing materials 5 a and 5 b ofdifferent particle diameter are dispersed, ahalf-column-cylindrical-lens-group 4 is formed.

Hereunder is a description of color shift of a transmission screen.

In a transmission screen not using a light diffusing material, whenprojected light from the projector passes through the screen, it is notdispersed by a light diffusing material, and directly reaches to theviewer side (refer to FIG. 14). Therefore, via the screen, tiny shiftsof R, G, B caused by slight differences in the color mixing opticalsystem of the projector are directly observed, and consequently colorshift becomes large.

In a conventional transmission screen using an organic light diffusingmaterial as the light diffusing material, when projected light from theprojector passes through the screen, it is dispersed by the lightdiffusing material and reaches to the viewer side (refer to FIG. 15).Therefore, via the screen, tiny shifts of R, G, B caused by slightdifferences in the color mixing optical system of the projector arerespectively dispersed and observed.

In a transmission screen of the present invention using a lenticularlens sheet which necessarily contains an inorganic light diffusingmaterial, when projected light from the projector passes through thescreen, it is dispersed by the light diffusing material and reaches tothe viewer side (refer to FIG. 13). Therefore, via the screen, tinyshifts of R, G, B caused by slight differences in the color mixingoptical system of the projector are respectively dispersed and observed.

The base material constituting the light diffusing layer of thetransmission screen, often includes a plastics material, and attentionis given to the refractive index difference between the base materialand the light diffusing material. Comparing the case using an organiclight diffusing material and the case using an inorganic light diffusingmaterial, the former has less refractive index difference between thebase material, and the latter has more refractive index differencebetween the base material. The greater the refractive index differencebetween the base material and the light diffusing material, the widerthe range where the same chromaticity is observable, and there is aneffect to reduce color shift.

Next, for the inorganic light diffusing material which forms the lightdiffusing layer of the lenticular lens sheet in the present invention,it is preferable to have an irregular shape. The function for reducingcolor shift by using an irregular shape is described.

The diffusion angle is determined corresponding to the particle diameterof the light diffusing material. FIG. 16 is a comparison of a diffusionangle curve 10 for the case of a globular shaped light diffusingmaterial, and a diffusion angle curve 9 for the case of an irregularshaped light diffusing material. In the case of the irregular shapedlight diffusing material, it is possible to take a wide diffusion angle.The greater the diffusion angle, the wider the range where the samechromaticity is observable, and there is an effect to reduce colorshift.

Next is a description to compare the dispersibility of the lightdiffusing material between a case where light diffusing materials of thesame particle diameter are dispersed and a case where two or more kindsof light diffusing materials of different particle diameter aredispersed.

In the case where light diffusing materials of the same particlediameter are dispersed, the light diffusing materials tend to bearranged in matrix form in the base material and thus maintain a stablecondition.

In the case where two or more kinds of light diffusing materials ofdifferent particle diameter are dispersed, the stable matrix form arraystate comprising light diffusing materials of the same particle size isdisturbed by at least one kind of light diffusing material of differentparticle size. As a result, the light diffusing materials become in anunstable array state and dispersibility is increased.

By making at least one kind of light diffusing material for dispersingin the light diffusing layer of the lenticular lens sheet of the presentinvention an inorganic light diffusing material, and taking a widerefractive index difference between the base material composed oforganic material and the light diffusing material, there is an effect toreduce color shift. Consequently, a transmission screen that reducescolor shift can be realized.

By making the light diffusing material for dispersing in the lightdiffusing layer of the lenticular lens sheet of the present invention,an inorganic light diffusing material of irregular shape, a transmissionscreen that reduces color shift can be realized.

By dispersing two or more kinds of light diffusing materials ofdifferent particle diameter in the light diffusing layer of thelenticular lens sheet of the present invention, a transmission screen ofgood dispersibility can be realized.

In the present invention, by making the light diffusing material in thelight diffusing substrate have a combination of at least two or morekinds differing in shape, mean particle diameter, or material, and alsomaking at least one kind of material be composed of an inorganicmaterial, a transmission screen of good dispersibility of the lightdiffusing material and that reduces color shift can be realized.

Hereunder is a description of an example of the second embodiment of thepresent invention for the case where a liquid crystal projector is usedas an image display.

EXAMPLE 6

In a configuration from the light source side of a Fresnel lens sheetwithout a light diffusing material, and a lenticular lens sheet having alight diffusing layer kneaded with two kinds of globular inorganic lightdiffusing materials of different particle diameter (refer to FIG. 8A),the chromaticity was measured and evaluated by a color brightnessphotometer. The evaluation results are shown in FIG. 17.

FIG. 17 is a graph showing the chromaticity of an XYZ calorimetricsystem (x, y) which becomes a base for respective colorimetric systemsas a CIE standard calorimetric system.

Here x (horizontal), y (horizontal) denote chromaticity (x, y) measuredin the horizontal direction, and x (vertical), y (vertical) denotechromaticity (x, y) measured in the vertical direction. The verticalaxis in the graph denotes the size of chromaticity (x, y). Compared toexample 3, differences in chromaticity are remarkably reduced.

EXAMPLE 7

In a configuration from the light source side of a Fresnel lens sheetwithout a light diffusing material and a lenticular lens sheet having alight diffusing layer kneaded with two kinds of globular inorganic lightdiffusing materials of different particle diameter and one kind ofirregular shaped inorganic light diffusing material (refer to FIG. 9),the chromaticity was measured and evaluated by a color brightnessphotometer. The evaluation results are shown in FIG. 17. Compared toexample 3, differences in chromaticity are remarkably reduced.

EXAMPLE 8

In a configuration from the light source side of a Fresnel lens sheetwithout a light diffusing material, and a lenticular lens sheet having alight diffusing layer kneaded with one kind of globular organic lightdiffusing material and one kind of inorganic light diffusing materialwith a smaller particle diameter than that of the organic lightdiffusing material (refer to FIG. 10), the chromaticity was measured andevaluated by a color brightness photometer. The evaluation results areshown in FIG. 17. Compared to example 3, differences in chromaticity areremarkably reduced.

EXAMPLE 9

In a configuration from the light source side of Fresnel lens sheetwithout a light diffusing material, and a lenticular lens sheet a lightdiffusing layer kneaded with one kind of globular organic lightdiffusing material, one kind of inorganic light diffusing material witha smaller particle diameter than that of the organic light diffusingmaterial, and one kind of irregular shaped inorganic light diffusingmaterial (refer to FIG. 11), the chromaticity was measured and evaluatedby a color brightness photometer. The evaluation results are shown inFIG. 17. Compared to example 3, differences in chromaticity areremarkably reduced.

COMPARISON EXAMPLE 3

In a configuration from the light source side of a Fresnel lens sheetwithout a light diffusing material and a lenticular lens sheet having alight diffusing layer kneaded with one kind of globular organic lightdiffusing material (refer to FIG. 12), the chromaticity was measured andevaluated by a color brightness photometer. The evaluation results areshown in FIG. 17. The differences in chromaticity are fairly large.

Next is a description of a third embodiment of the present invention.

The transmission (light diffusion) screen according to the presentinvention is comprised of a light diffusing layer comprising atransmissive resin dispersed with light diffusing material (lightdiffusive particles), and a transmissive base material, and is set sothat the refractive index of the resin other than the light diffusingmaterial is higher than the refractive index of the light diffusingmaterial.

Here, for the refractive index ratio of the resin other than the lightdiffusing material and the particles, if the former is 1, it ispreferable to control so that the latter is in a range of 0.7 to 1, morepreferably in a range of 0.9 to 1, and even more preferably in a rangeof 0.93 to 1.

Furthermore, for the refractive index difference of the resin other thanthe light diffusing material and the light diffusing material, it ispreferable to control so that the refractive index difference is in arange of 0 to 0.2, more preferably in a range of 0 to 0.1, and even morepreferably in a range of 0.001 to 0.05.

The light diffusing material used for the transmission screen of thepresent invention is preferably one with a refractive index ratio andrefractive index difference with respect to the transmissive resin otherthan the light diffusing material, which satisfies the above conditions,and which is transparent and has excellent dispersibility in the resinlayer.

Furthermore, the shape is preferably globular, and in particular aspherical shape is more preferable. The mean particle diameter ispreferably in a range of 1 to 30 μm, and more preferably in a range of 5to 20 μm.

Moreover, the standard deviation of the mean particle diameter accordingto a laser diffraction scattering method is preferably less than 6 μm,and more preferably around 5 μm.

The dosage is preferably in a range of 5 to 40 parts by weight for 100parts by weight of the light diffusing layer, and more preferably in arange of 10 to 30 parts by weight.

Examples of particles used for such light diffusing material includespecifically, particles of organic high molecular compounds comprisingacrylic resin, polyurethane resin, and polyamide resin, and particles ofinorganic compounds such as silica.

The transmissive resin other than the light diffusing material used forthe transmission screen of the present invention is preferably one witha refractive index ratio and refractive index difference with respect tothe light diffusing material, which satisfies the above conditions, andwhich is transparent and has excellent dispersibility of the particles,and also has excellent adhesiveness to the transmissive base material.

Furthermore, it is even more preferable if it has excellent flexibilityto avoid cracking when being bent.

The material for the resin layer is not specifically limited as long asit satisfies the above conditions. Examples include thermoplasticresins, thermosetting resins, and energy-beam-curable-resins such asultraviolet-ray-curable-resins.

Furthermore, in order to avoid contrast decrease, the thickness of theresin layer, that is, the thickness of the light diffusing layer, ispreferably in a range of 1 to 60 μm, and more preferably in a range of20 to 50 μm.

The material of the transmissive material of the transmission screen ofthe present invention is preferably a transparent base material,including for example plastics base material, however, it is notspecifically limited.

For the plastics, a thermoplastic resin, a thermosetting resins, anenergy-ray-curable-resin such as an ultraviolet-ray-curable-resin can beused. Examples include; polyolefin resin such as polyethylene,polypropylene, polyolefin resin such as polyethylene terephthalate,cellulose resins such as triacetylcellulose and butyl cellulose, andpolystyrene, polyurethane, vinyl chloride, acrylic resin, polycarbonateresin, polyester resin, and the like.

The thickness of the base material is not specifically limited. However,from the aspect of lightening and cost reduction, it is preferably in arange of 10 to 1000 μm, and more preferably in a range of 30 to 500 μm.

Further, in order to increase the adhesiveness with the light diffusinglayer, it is possible to perform various treatments on the surface ofthe base material. Examples of treatment methods includes coronatreatment, anchor treatment, saponification treatment, treatment bysilane coupling agent, and the like.

Hereunder is a description using the embodiments, of a transmissionscreen which uses a lenticular lens sheet having a transmission screenaccording to the present invention.

Here, a liquid crystal projector is used as an image display, and theconfiguration is from the light source side, a Fresnel lens sheetwithout a light diffusing material, and a lenticular lens sheet having atransmission screen of the present invention.

EXAMPLE 10

In a transmission screen wherein the refractive index of the resin otherthan the light diffusing material dispersed in the light diffusing layeris set higher than the refractive index of the light diffusingparticles, and the refractive index ratio between the transmissive resinother than the light diffusing material is 0.97, and the refractiveindex difference is 0.05, and which uses a transmission screen having alight diffusing layer wherein the light diffusing material comprises anorganic high molecular compound composed of acrylic resin, and thematerial of the resin comprises an acrylic resin, hot bar andscintillation were evaluated by visual observation. The evaluationresults are shown in Table. 1.

EXAMPLE 11

In a transmission screen wherein the refractive index of the resin layerother than the light diffusing material dispersed in the light diffusinglayer is set higher than the refractive index of the light diffusingmaterial, and the refractive index ratio between the transmissive resinother than the light diffusing material is 0.95, and the refractiveindex difference is 0.08, and which uses a transmission screen having alight diffusing layer wherein the light diffusing material comprises anorganic high molecular compound composed of acrylic resin, and thematerial of the resin comprises an acrylic resin, hot bar andscintillation were evaluated by visual observation. The evaluationresults are shown in Table. 1.

COMPARATIVE EXAMPLE 4

In a transmission screen wherein the refractive index of the resin layerother than the light diffusing material dispersed in the light diffusinglayer is set lower than the refractive index of the light diffusingmaterial, and the refractive index ratio between the transmissive resinother than the light diffusing material is 1.05, and the refractiveindex difference is 0.08, and which uses a transmission screen having alight diffusing layer wherein the light diffusing material comprises anorganic high molecular compound composed of acrylic resin, and thematerial of the resin comprises an acrylic resin, hot bar andscintillation were evaluated by visual observation. The evaluationresults are shown in Table. 1.

TABLE 1 Hot bar Scintillation Example 10 A A Example 11 B A Comparativeexample 4 D C

In Table. 1, “A” denotes that the respective observations were within anacceptable range and the image quality was excellent. “B” denotes thatthe respective observations were within the acceptable range and theimage quality was good. “C” denotes that the respective observationswere outside of the acceptable range and the image quality was poor. “D”denotes that the respective observations were generated and the imagequality was very poor.

From the results of Table. 1, it is confirmed that in the transmissionscreen of the present invention, hot bar is reduced and scintillation ismitigated, compared to the screen of comparative example 4.

Next is a description of a fourth embodiment of the present invention.

FIG. 18 shows a cross-section of a liquid crystal projection-type rearprojection television, as an example of a display device of the presentinvention.

A rear projection television 300 is normally constructed such that imagelight projected from a projector having a light source 301, an opticalequipment section 302, a liquid crystal panel 303 and a projection lens304, reaches a viewer via a mirror 305 and a screen 306 including aFresnel lens sheet having a Fresnel lens section and a lenticular lenssheet having a lenticular lens section.

For the screen (transmission screen) 306 used for the above rearprojection television 300, directivity which disperses widely in thehorizontal direction and slightly narrower in the vertical directionthan in the horizontal direction is demanded. Therefore, generally, alenticular lens is used as the diffusion element in the horizontaldirection, and a light diffusing substrate in which light diffusingmaterial is dispersed, is used as the diffusion element in the verticaldirection.

In the present embodiment, as the screen 306, the transmission screendescribed for the first to third embodiments is employed. Therefore itbecomes possible to provide a display device that is bright with highresolution, that has a wide viewing angle in both the horizontal andvertical directions, that is superior in contrast, that enables viewingof sharp images, and further that reduces color shift.

The present invention is not limited to the above embodiments, andvarious modification can be further made within a range which does notdepart from the gist of the present invention.

For example, in the aforementioned embodiment as shown in FIG. 1A andFIG. 1B, the transmission screen is configured to have a Fresnel lenssheet and a lenticular lens sheet, and the light diffusing substrate inwhich light diffusing material is dispersed, is applied to at least oneof the Fresnel lens sheet and the lenticular lens sheet. However, thepresent invention is not limited to this. For example, it is alsopossible to apply the light diffusing substrate (light diffusing sheet)of the present invention to a transmission screen of anotherconfiguration.

FIG. 19A and FIG. 19B are cross-sections showing an example where thelight diffusing substrate of the present invention is applied to atransmission screen of another configuration.

In FIG. 19A, an image light source is arranged on the right side of thedrawing, and a viewer is positioned on the left side of the drawing. Inthis transmission screen 400, sequentially in a direction from theviewer side to the image light source, is arranged stuck together, alight diffusing substrate (a sheet containing a light diffusingmaterial, a light diffusing sheet) 401, unit lenses 402, and a basesheet 403. Furthermore, part of the cross-sectional triangles betweenthe oblique sides of the adjacent respective unit lenses 2, is filledwith a material having a lower refractive index than that of the unitlenses 402. Hereunder, the parts filled with the material of lowerrefractive index are denoted by the “lower refractive index sections404”, and as necessary, the unit lenses 402 are denoted by the “higherrefractive index sections 402”.

The ratio between a refractive index N1 of the higher refractive indexsection 402 and a refractive index N2 of the lower refractive indexsection 404 is set within a predetermined range in order to obtain theoptical characteristics of the transmission screen 400. Furthermore, theangle between the oblique side where the lower refractive index section404 and the higher refractive index section 402 come in contact witheach other, and a normal to the outgoing light surface (which isparallel to the vertical incident light for the light diffusing sheet)is made a predetermined angle q.

The lower refractive index section 404 is colored to a predetermineddensity by pigments such as carbon, or by a predetermined dyestuff.Furthermore, the light diffusing substrate 401 and the base sheet 403are constituted by materials having approximately the same refractiveindex as that of the higher refractive index section 402.

Next is a brief description of an optical path of incident light intothe unit lens 402, with reference to FIG. 19A. In FIG. 19A and FIG. 19B,optical paths of light L1 to L4 are schematically shown.

A vertical light L1 which is incident from the image light source sideto near the center of the unit lens 402, passes straight through theinterior of the transmission screen 400 and to reach a viewer. Avertical light L2 which is incident from the image light source side tonear the edge of the unit lens 402, is totally reflected at the obliqueside due to the refractive index difference between the higherrefractive index section 402 and the lower refractive index section 404,and passes out to the viewer side with a predetermined angle. A light L3which is incident at an angle from the image light source side to nearthe edge of the unit lens 402, is totally reflected at the oblique sideand passes out to the viewer side with a larger angle in the oppositedirection to when incident. A stray light L4 which is incident on theoblique side with a larger angle than a predetermined angle, is notreflected in spite of the refractive index difference between the higherrefractive index section 402 and the lower refractive index section 404,and is incident into the interior of the lower refractive index section404. Since the lower refractive index section 404 is colored, the straylight is absorbed in the lower refractive index section 404 and does notreach to the viewer side. In this manner, a screen which has a wideviewing angle in the horizontal direction and which is high in contrastand brightness can be obtained.

Furthermore, in FIG. 19A, the light diffusing substrate 401 of thepresent invention is characterized in that; it mainly includes anorganic material, a light diffusing layer contains two or more kinds oflight diffusing material which differ in at least one of shape, meanparticle diameter, and material, and at least one of the light diffusingmaterials includes an inorganic material.

Furthermore, FIG. 19B has approximately the same configuration as inFIG. 19A. However, a light diffusing substrate 501 of the presentinvention is characterized in that; it mainly comprises an organicmaterial, a light diffusing layer contains two or more kinds of lightdiffusing material which differ in at least one of shape, mean particlediameter, and material, and at least one of the light diffusingmaterials includes an inorganic material.

According to these configurations, it becomes possible to enhance evenmore the effect where due to the above configuration of the lowerrefractive index section 404 and the higher refractive index section402, a wider viewing angle in the horizontal direction is obtained andcontrast and brightness are high.

1. A transmission screen comprising: a Fresnel lens sheet through which light is projected from a projector as approximately parallel light; a lenticular lens sheet which receives the approximately parallel light passing through the Fresnel lens sheet, and which horizontally widens and emits the approximately parallel light using a group of cylindrical lenses; and a light diffusing substrate having a light diffusing layer, which is provided with the lenticular lens sheet, wherein the light diffusing substrate is mainly composed of an organic material, the light diffusing layer contains at least two kinds of light diffusing material which differ at least in any one of shape, mean particle diameter, or material, and at least one kind of light diffusing material of the light diffusing materials comprises an inorganic material.
 2. A transmission screen according to claim 1, wherein in the case where the shapes of at least two kinds of light diffusing material contained in the light diffusing layer are globular, the light diffusing layer contains a first light diffusing material with a mean particle diameter satisfying a range of 1 to 10 μm and a second light diffusing material with a mean particle diameter satisfying a range of 20 to 50 μm.
 3. A transmission screen according to claim 1, wherein in the case where at least one kind of light diffusing material contained in the light diffusing layer comprises an organic material, the mean particle diameter of the organic light diffusing material is larger than the mean particle diameter of an inorganic diffusing agent where the light diffusing material comprises an inorganic material.
 4. A transmission screen according to claim 1, wherein the at least two kinds of light diffusing material which differ at least in any one of shape, mean particle diameter, or material, contained in the light diffusing layer, further contain an inorganic light diffusing material of irregular shape.
 5. A display device of a type which forms a display light by projecting an illumination light onto image display elements in which a display image is regulated by transmission/non transmission (or, transmission/light diffusion) or selective reflection, equipped with a transmission screen according to claim 1, in combination with another lens sheet. 